1. Technical Field
The present invention relates in general to a system and method for calibrating a low vision device. More particularly, the present invention relates to a system and method for using a series of calibration steps to customize a low vision device for a user.
2. Description of the Related Art
Low vision is a term given to impairments that make it affect the ability of a person to correctly see objects. Low vision may include minor impairments such as color blindness, or a severe impairment such as macular degeneration.
Macular degeneration is a term used to refer to a group of disorders that affect the central portion of the retina and, as a result, the central vision. The most common forms of macular degeneration usually affect patients over the age of 65. These forms, which are often called “age-related macular degeneration”, are collectively the most common cause of legal blindness in developed countries. Age related macular degeneration is extremely prevalent with as many as one in ten patients over the age of 65 affected to some degree.
The inside of the eye is lined by three layers of tissue which each have a critical role in normal vision. The three layers are the retina, the retinal pigment epithelium (RPE), and the choroid. The retina is the first layer struck by light as it enters the eye and consists of a complex network of nervous tissue called photoreceptors. Photoreceptors convert light into electrical signals that are then amplified and processed by other cells before being sent to the brain through an optic nerve. The central part of the retina, called the macula, has a number of special structural features that allow images to be seen with very high resolution.
The retinal pigment epithelium (RPE) is the middle tissue layer of the eye and is one cell thick. The RPE provides metabolic support for photoreceptor cells and also removes old bits of cellular debris from the tips of the photoreceptor cells as they renew themselves. The choroid is the third tissue layer that is a rich network of blood vessels. These blood vessels supply oxygen and nutrients to the RPE and photoreceptor cells.
In macular degeneration, clumps of yellowish cellular debris, possibly of retinal origin, gradually accumulate within and beneath the RPE. These deposits are visible to a clinician looking inside the eye as small yellow dots known as drusen. With the passage of time, patches of RPE cells may die from the accumulating debris. As a result, bare spots form in the RPE that are referred to as “geographic atrophy”. RPE areas with geographic atrophy stop providing metabolic support to overlying photoreceptor cells. In turn, the overlying photoreceptor cells seize functioning which brings about vision loss in the corresponding retina area.
Although reduced central or reading vision is most common, low vision may also result from decreased side (peripheral) vision, or a loss of color vision. In addition, low vision may result in a person losing the ability to adjust to light, contrast or glare. Vision assistance devices are available for people with low vision issues. These devices are typically scanners or cameras connected to a head mounted display (HMD) or closed circuit television (CCTV). Low vision devices generally provide magnification, basic focus, and contrast features that enable a low vision user to see words, a person's face, and objects. A challenge found with existing low vision devices is that they do not provide image-processing functions for increased image enhancement. For example, a low vision device may not distinguish specific colors to a person that is colorblind. What is needed, therefore, is a way to customize a low vision device corresponding to the type and state of a user's vision impairment.